Optimizing Conical Intersections without Derivative Coupling Vectors: Application to Multistate Multireference Second-Order Perturbation Theory (MS-CASPT2)

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• 作者：Benjamin G. Levine ; Joshua D. Coe ; Todd J. Mart&iacute ; nez
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：January 17, 2008
• 年：2008
• 卷：112
• 期：2
• 页码：405 - 413
• 全文大小：350K
• 年卷期：v.112,no.2(January 17, 2008)
• ISSN：1520-5207

文摘

We introduce a new method for optimizing minimal energy conical intersections (MECIs), based on a sequentialpenalty constrained optimization in conjunction with a smoothing function. The method is applied to optimizeMECI geometries using the multistate formulation of second-order multireference perturbation theory (MS-CASPT2). Resulting geometries and energetics for conjugated molecules including ethylene, butadiene, stilbene,and the green fluorescent protein chromophore are compared with state-averaged complete active space self-consistent field (SA-CASSCF) and, where possible, benchmark multireference single- and double-excitationconfiguration interaction (MRSDCI) optimizations. Finally, we introduce the idea of "minimal distance conicalintersections", which are points on the intersection seam that lie closest to some specified geometry such asthe Franck-Condon point or a local minimum on the excited state.